Positive seal coupling internal joining press

ABSTRACT

This invention is a new device for installing press fit couplings to join steel pipelines. This apparatus is a joining press which fits inside the pipes to be joined and grabs them on their inside surfaces. It then pulls the pipes together, forcing the pipe ends into the coupling. The invention is comprised of two hydraulically operated grippers to grip the pipe and a hydraulically operated cylinder to pull the pipes together. The entire press is controlled using only two hydraulic lines. The grippers can be retracted and the apparatus moved within the pipeline from one joint to the next.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to couplings used to join sections of pipetogether into a continuous pipeline.

2. Description of Related Art

The conventional way to assemble pipelines is to weld individual piecesof pipe together For large diameter pipes, however, welding is a slowprocess. One way to avoid the high cost of welding is to use asleeve-type coupling to fit over the two ends of the two pipes beingjoined.

Several sleeve-type couplings have been developed. Representative isU.S. Pat. No. 4,328,983 issued to Jack E. Gibson. The coupling consistsof a sleeve having an internal diameter slightly smaller than theexternal diameter of the pipe sections to be joined. Forcing one end ofa pipe section into each end of the coupling sleeve effects a press fit,sealed connection between each pipe section and the coupling.

Installation of couplings on pipe sections can be accomplished with amachine disclosed in U.S. Pat. No. 4,328,608 also issued to Jack E.Gibson. This machine grabs the outside of the pipe, grabs the end of thecoupling, then forces the pipe into the inside of the coupling using twohydraulic cylinders which generate a force of approximately 120,000 lbs.Once the coupling is installed onto one end of a pipe, a second pipe canbe installed, completing the joint. A major problem with this machine isthat the hydraulic rams used to exert the forces necessary to accomplishthe press fit must be mounted on a massive base which, in turn, canwithstand the forces without becoming deformed. Consequently, thismachine can only be used where there is ample, unobstructed space forits operation. Often it is used to construct underground oiltransmission pipelines. The pipeline is assembled on the surface andthen lowered into a trench. There normally is plenty of space around thetrench, so the large size of the installation equipment is not aproblem.

There are many instances where space is limited and the standard joiningpress cannot be used. One example is pipe containing high voltageelectric transmission cables in an urban environment. Urban pipe-typeinstallations are typically encumbered by frequent crossings of otherutilities and by trench shoring, both of which prevent the lowering of asurface joined pipeline directly into the trench. Cramped quarters andthe need to minimize trench size also prohibit placing the existingpress into the trench for making the joint.

One solution to this problem is disclosed in U.S. Pat. No. 4,389,763issued to Richard O. Marsh, Jr. The device used by Marsh has a slottedend plate which abuts the end of the pipe section opposite that to beinserted in the coupling. A hollow piston rod is attached to the endplate via a hydraulic cylinder and extends inside the pipe for theentire length of the pipe section. The hollow piston rod ends with amulti-fingered pawl mechanism which is used to grip a couplingpreviously installed on the other section of pipe. The coupling usedwith this device is a cylinder with annular grooves machined or cast inthe ends of the cylinder. The ends of the pipe sections are press fitinto the grooves on either end of the cylindrical sleeve. When thecoupling is installed on one end of a pipe section, the resultingprofile of the internal wall of the pipe-coupling combination containsan abrupt step formed by the end of the coupling sleeve. The pawlmechanism grips this step and the hydraulic cylinder puts the hollowpiston rod in tension, thus drawing the end of the pipe section into theannular groove of the coupling.

Although this device reduces the size of the installation machinery, ithas a number of significant drawbacks. The device is still quite largeand unwieldy because the piston rod must be as long as the section ofpipe being installed. The device cannot be used on pre-bent pipe becauseof the straight piston rod. Even if a flexible cable were substitutedfor the rigid piston rod, the device could not be used with bent pipebecause the force is applied to the ends of the pipe and theeccentricity of the bent pipe would cause it to fold. And finally, thecompleted pipeline contains numerous steps along its interior whichsignificantly increase pressure drop when the pipe is used to transportfluid or which significantly increase the chance of installation damageto insulation when the pipe contains electrical conductors.

It is an object of the invention to provide a small, compact pipecoupling apparatus which can be used in the confined spaces of a pipetrench.

Another object of the invention is to provide a pipe coupling apparatuswhich can be used to join pre-bent sections of pipe.

It is yet another object of the invention to provide a pipe couplingapparatus that results in a pipe joint without abrupt steps in theinterior surface of the pipeline.

These and other objects are accomplished by the subject invention.

SUMMARY OF THE INVENTION

This invention is a new device for installing sleeve type couplings tojoin steel pipelines. The invention comprises a joining press which fitsinside the pipes to be joined and grabs them on their inside surfaces.It then pulls the pipes together, forcing the ends of each pipe into thecoupling. The invention is comprised of two hydraulically operatedgrippers to grip the pipe and a hydraulically operated cylinder to pullthe pipes together. The entire press is controlled using only twohydraulic lines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the operational procedure used in joining pipe with theinvention and the relationship between the various parts of theinvention. FIG. 1a shows the press in position to make a joint. FIG. 1bshows the press gripping the two pipes to be joined. FIG. 1c shows thepress with the main cylinder retracted and the joint completed.

FIG. 2 is a view of the coupling adapter used in placing a coupling on apipe.

FIG. 3 is a cross sectional view of the outboard gripper of the presentinvention.

FIG. 4 is a cross sectional view of the main cylinder of the presentinvention.

FIG. 5 is a cross sectional view of the inboard gripper of the maincylinder.

FIG. 6 is a schematic drawing showing the hydraulic porting of thevarious parts of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1a, the invention, generally indicated as 10 isshown ready to join first pipe 1 to second pipe 2 with coupling 3. Themain cylinder 5 is positioned approximately inside the coupling 3 withits piston rod 4 in the fully extended position. The inboard gripper 7and outboard gripper 6 are in the retracted position. The second pipe 2is positioned close to the coupling 3. The hydraulic hose assembly,generally referred to as 8 is snaked through the second pipe 2 andconnected to the hydraulic power supply and valve package (not shown).

Referring now to FIG. 1b, after the press 10 and pipes 1,2 arepositioned, the inboard gripper 7 and outboard gripper 6 arehydraulically actuated. The inboard gripper 7 grips the first pipe 1 andthe outboard gripper 6 grips the second pipe 2. The main cylinder 5 isthen retracted so the piston rod 4 is drawn inside. This pulls the twopipes 1,2 together inside the coupling 3. When the two pipes 1,2 toucheach other the joining process is complete, and the completed joint isshown in FIG. 1c.

Reference is now made to FIG. 1c, which shows a completed joint. The twogrippers 6,7 are then retracted. The press 10 is then slid to the leftby a tension member or rope in the hydraulic hose assembly 8 and partwayout of the pipe 2 to get ready to make the next joint using coupling 9.Once the grippers 6,7 are retracted, the press rests on plastic skidpads 17 as shown in FIG. 1a. The skid pads 17 are made of a low-frictionmaterial and protect the pipe 2 from damage that would be caused if thegripping teeth of the grippers 6,7 contacted the pipe 2 as it slid downit. When the grippers 6,7 are engaged, they extend outward beyond theskid pads 17 and grip the pipe.

Indicated above is merely one of many possible permutations forconstructing a pipeline. Other possible permutations include assemblinqpipes from left to right instead of from right to left, and having thecoupling 3 on the second pipe 2 instead of on the first pipe 1. Allpermutations can just as easily be handled with this invention.

It should be further noted that in the sequence shown in FIG. 1a-c, thecoupling 3 is depicted as having been previously attached to the firstpipe section 1, prior to completing the pipeline joint. Prejoining ofcoupling 3 to pipe section 1 could have been done by a variety of means,including means employing this invention (as described below and in FIG.2). Alternative means of preattachment of coupling 3 to pipe section 1could include, but need not be limited to welding, threaded engagement,or integral construction as in the so-called "bell and spigot" ormale-female pipe geometry well known to pipeline practitioners.

Alternatively, it is possible with the subject invention to joincoupling 3 to pipe sections 1 and 2 simultaneously, in which case thestroke of main cylinder 5 would need to be at least approximately twiceas great as in the configuration depicted in FIGS. 1a-c.

Referring now to FIG. 2, a coupling adapter 11 is shown which can beused to place a coupling 12 on the end of a pipe 14 in situations wherethe coupling 12 has not been preinstalled. The coupling 12 is supportedby the outside diameter of the adapter 11. The coupling 12 is pushedonto the pipe 14 by the shoulder section 15 of the adapter 11. Theadapter 11 is in turn grabbed by the inboard gripper 7 which is pulledby the main cylinder 5. The coupling 12 is pushed onto the pipe 14 untilthe edge 16 of the adapter 11 contacts the end of the pipe 14. Thisassures that exactly half of the coupling 12 overlaps the pipe 14 andthe other half of the coupling 12 is ready to accept the other pipe (notshown), forming the joint.

This situation is very similar to a normal procedure where two pipes arebeing joined, as can be seen by comparing FIGS. 2 and 1b. In FIG. 2, theadapter 11 takes the place of the first pipe 1 of FIG. 1b. Otherwise theprocedure is the same.

Turning now to FIG. 3, the mechanical details of the outboard gripper 6are indicated. The parts of the gripper 6 which actually grip the insideof the pipe (not shown) are the slips 21. There are four slips 21, eachforming an approximately 90 degree arc, surrounding a mandrel 22. Themandrel 22 is connected to the piston rod 4 of the main cylinder 5 viathreads 23. Pulling force (in a horizontal direction to the right) istransferred from the piston rod 4, through the threads 23, to themandrel 22. It is then transferred from the mandrel 22 to the slips 21through four tapered cone sections 24 and finally from the slips 21 tothe pipe (not shown) through a buttress thread 25 on the outside of theslips 21.

FIG. 3 shows the gripper 6 in the retracted (or released) position, inwhich its outside diameter is approximately 0.75 inches less than theinside diameter of the pipe being gripped. To grip the pipe, the slips21 are pushed to the left by actuator bars 26 and 27. When the slips 21are pushed to the left relative to the mandrel 22, the tapered conesections 24 of the mandrel 22 push the slips radially outward until theycontact and can grip the inside of the pipe (not shown). The angle ofthe tapered cones 24 is such that a force to the right from piston rod 4tends to increase the contact force between the slips 21 and the pipe,enabling the slips 21 to grip the pipe harder.

To release the gripper 6, the slips 21 are pushed to the right. Fourgarter springs 28 then pull the slips 21 radially inward as the slips 21maintain contact with the tapered cone sections 24. This reduces theoutside diameter of the gripper 6 so that the slips 21 no longer contactthe pipe and the gripper 6 (along with the entire joining press) mayslide down the pipeline to make the next joint.

The actuator bars 26 and 27 reside partly inside a piston 29. Thevertical bar 26 fits snugly inside a slot in the piston 29 and extendsoutward through slots 30 in the mandrel 22. The horizontal bar 27 alsofits snugly inside a slot in the piston 29 and also fits snugly througha slot in the vertical bar 26. A set screw 31 holds the two actuatorbars 26, 27 together and prevents relative motion between the two bars26, 27 and the piston 29. The actuator or piston subassembly 26, 27, 29is able however to slide horizontally relative to the mandrel 22 becausethe slots 30 are longer than the actuator bars 26, 27.

Motion of the piston 29 is controlled by the hydraulic fluid in twocavities 32, 33 on either side of it. If fluid enters the left cavity 32and exits the right cavity 33, the piston will be pushed to the rightand the gripper will retract. If fluid enters the right cavity 33 andexits the left cavity 32, the piston will be pushed to the left and thegripper will engage.

Hydraulic fluid enters and leaves the left cavity 32 via quickdisconnect 34, manifold block 35, feed tube 36 and port 37. Hydraulicfluid enters and leaves the right cavity 33 via quick disconnect 38,manifold block 35, feed tube 39 and port 40. In the preferred embodimentof the invention, there are a multiplicity of ports 37, 40 and feedtubes 36, 39, increasing the flow area and decreasing the fluid flowvelocity. Although not shown in the figure, in the preferred embodimentthe manifold block 35 splits the flow from a single quick disconnect 34into a multiplicity of feed tubes 36 and splits the flow from a singlequick disconnect 38 into a multiplicity of feed tubes 39.

It is desirable to the operation of this invention to keep the gripperin the fully released position unless the hydraulic pressure of thefluid at quick disconnect 38 exceeds a certain threshold value(approximately 400 psi in the preferred embodiment). This is so the maincylinder may retract at a low pressure (less than 400 psi) withoutengaging the grippers as will be explained when discussing the hydraulicoperation of the invention. This feature is accomplished by means ofspringloaded check valve 42 and check valve 43.

When the piston 29 is in the fully retracted position shown in FIG. 3,fluid from port 40 must flow through a drilled hole 41 in the piston 29and through a spring-loaded check valve 42 before it may enter the rightcavity 33 and move the piston. Thus the piston will not actuate thegripper until the pressure at port 40 exceeds the preset value of thespring-loaded check valve. Once the piston moves and the seal 44 movespast the port 40, fluid may enter cavity 33 directly, without flowingthrough drilled hole 41 and without the pressure drop caused byspring-loaded check valve 42. Fluid may always leave cavity 33 and enterport 40 without any restriction or pressure drop. When the piston in theposition shown in FIG. 3, fluid leaves via check valve 43 and hole 41.When the seal 44 is to the left of port 40, fluid may enter port 40directly.

Hydraulic fluid from quick disconnects 38, 34 is also used to controlthe main cylinder (5 in FIG. 1) and the outboard gripper (7 in FIG. 1).Fluid flows from quick disconnect 38, through the manifold 35 andmandrel 22 and then into a groove 46 in an internal manifold 45. Fromthis groove 46 it enters a hole 47 and feed tube 48 and finally goesinto the center hole of the main cylinder's 5 piston rod 4. Fluid fromquick disconnect 34 flows through the manifold 35 and mandrel 22 andthen into a groove 49 of internal manifold 45. From there it enters aface groove 50 and then goes into a feed hole 52 of the piston rod 4.Fluid passage beyond the piston rod will be described later. It isimportant to note that these flows are in parallel with the flows intothe cavities 32 and 33 which actuate the gripper.

An eyebolt 53 and locknut 54 are threaded into the manifold 35 and usedfor pulling the entire invention down the pipeline. An end plug 55 isthreaded into the mandrel 22 to plug the end of cavity 32.

Because of the many hydraulic passages and cavities, there are manyseals used in the gripper 6. There are many different ways to seal thecomponents and many kinds of seals, but in the preferred embodiment, thefollowing seals are used. An 0-ring seal and modular backup 56 is usedin the mandrel 22 to seal the cavity 32. Also sealing cavity 32 is polyseal and backup 57. A seal 58 is used to scrape the mandrel bore 59 tokeep dirt which enters slot 30 from contacting seal 57. The other sideof piston 29 uses identical seals 58 and 57 in similar roles. A seal 44mentioned previously is used to seal the two ends of spring-loaded checkvalves 42 and check valve 43.

An O-ring 60 seals the cavity 33 from groove 46. An 0-ring seal 61 andtwo modular back-ups seal groove 46 from groove 49. O-ring seal and twomodular back-ups 62 seals feed hole 48 from groove 50. 0-ring seal 63seals grooves 49 and 50 from the external environment. 0-ring seals 64in a static face seal configuration seal ports in the manifold from theexternal environment.

Now please refer to FIG. 4, which shows a cross section of the maincylinder, item 5 in FIG. 1. The main cylinder is the device whichgenerates motion of the two pipe grippers (items 6 and 7 in FIG. 1). Theoutboard gripper (item 6 in FIG. 1) is attached to the piston rod 4 withthreads 23. The inboard gripper (item 7 in FIG. 1) is attached to theend cap 70 with threads 71. Attached to piston rod 4 is the piston 72.

Motion of the piston 72 is generated by fluid flow into and out of rodend cavity 73 and cap end cavity 74. Fluid flows into and out of cavity73 through feed holes 77, 51 and port 75. Port 75 is connected into theoutboard gripper (6 in FIG. 1). Fluid flows into and out of cavity 74through port 76, feed hole 52 and port 76. Port 76 is connected into theoutboard gripper (6 in FIG. 1).

Fluid to control the inboard gripper (7 in FIG. 1) gets there by flowingthrough the main cylinder 5. Fluid which enters port 75 can also exitport 79 via feed hole 51, tube 81, and feed hole 82 and flow into theinboard gripper. Fluid which enters port 76 can also exit port 80 viafeed hole 52, cavity 74 and feed hole feed hole 83 and flow into theinboard gripper. It is important to note that fluid flow into theinboard gripper is done in parallel with flow into the main cylinder 5.Thus the grippers (6,7 in FIG. 1) can be actuated without moving themain cylinder 5 and vice versa.

The rod end cap 84 contains and 0-ring seal 85 and polypak seal 86 toseal cavity 73 from the external environment. It also contains a rodwiper 87 to clean the rod 4 as it enters the cap 84. The end cap 70contains an 0-ring seal 89 to seal cavity 74 from the environment andthreads 88 for attaching feed tube 81.

The piston contains a seal 90 and 0-ring seal 94 to seal cavity 73 fromcavity 74 and a wear ring 91 to minimize wear of the inside surface ofcylinder tube 92. Seal 93 seals cavity 74 from feed hole 51. A setscrew95 is used to prevent unscrewing of piston rod 4 from piston 72.

FIG. 5 shows a cross sectional view of the inboard gripper, item 7 inFIG. 1. The inboard gripper is almost identical to the outboard grippershown in FIG. 3. Because of this, a detailed description will not begiven. The text below will concentrate on the differences between thisgripper and the outboard gripper. The only mechanical difference is thatan end cap 95 of the inboard gripper replaces the manifold 35 of theoutboard gripper. The end cap 95 blocks the ports 97,98 and is fastenedto the mandrel 99 by bolts 96.

Functionally, the differences are also very small. The only differenceis the porting and the direction of fluid flow. Fluid enters and exitsthe inboard gripper 7 through ports 100 and 101 from the main cylinder.From these ports fluid is directed to the piston actuation cavities 102,103 in the reverse direction that it occurs in the outboard gripper. Allother functions of the two grippers are identical.

Referring now to FIG. 6, the complete hydraulic porting of the inventionis shown. The hydraulic cavities 32 and 103 which release the grippers 6and 7 and the cavity 74 which extends the main cylinder 5 are allconnected to port 34. Thus pressurizing port 34 will usually extend themain cylinder 5 and release the grippers 6,7. Special cases where thisdoes not occur will be described later The hydraulic cavities 33 and 102which engage the grippers 6,7 and the cavity 73 which retracts the maincylinder 5 are all connected to port 38. Thus pressurizing port 38 willusually retract the main cylinder 5 and engage the grippers 6,7. Specialcases where this does not occur will be described later. The grippers6,7 and the main cylinder 5 are connected in parallel, so that it ispossible to move the main cylinder 5 without moving the gripperactuation pistons 29, 104, and vice versa.

The hydraulic operation of the invention proceeds as follows. First, themain cylinder is extended and the grippers are released by pressurizingport 34 and connecting port 38 to the reservoir tank (not shown) so thatfluid may exit at low pressure.

Next, the grippers 6,7 are engaged without moving the main cylinder 5.In the preferred embodiment this is done by maintaining 9000 psi at port38 and 6800 psi at port 34. Since the gripper actuation pistons 29, 104have equal areas on both sides, the pressure difference will cause themto move and engage the grippers 6,7. The piston 72 of the main cylinder5, however, does not have equal areas exposed to the pressure incavities 73 and 74. Because of the rod 4, the area exposed to pressurein cavity 73 is only 0.75 times the area exposed to cavity 74 (in thepreferred embodiment). Thus if cavity 73 has 9000 psi pressure in it,the piston 72 will remain in the extended position as long as thepressure in cavity 74 is greater than (0.75×9000) or 6750 psi. Since thepressure in cavity 74 is 6800 psi, the main cylinder 5 will remain inthe extended position.

The next operation requires the main cylinder 5 to retract while thegrippers 6,7 remain engaged. This is done by pressurizing port 38 andconnecting port 34 to the hydraulic reservoir tank.

The next operation is to release the grippers 6,7 and extend the maincylinder 5. This is done by pressurizing port 34 and connecting port 38to the reservoir tank (not shown).

The next operation is to retract the main cylinder 5 without engagingthe grippers 6,7. This is accomplished using the spring loaded checkvalve 42 and regular check valve 43 in outboard gripper 6. The inboardgripper 7 has identical components. Therefore the following descriptionof the outboard gripper's 6 operation will also apply to the inboardgripper 7. In the preferred embodiment the spring loaded check valve isset at approximately 400 psi. Therefore hydraulic fluid will not be ableto enter cavity 33 and engage the gripper 6 unless the pressure in port38 is greater than 400 psi. Under normal noload conditions, the maincylinder 5 will be able to retract at a pressure of approximately100-200 psi. Therefore if the pressure at port 38 is controlled to beless than or equal to 300 psi the main cylinder 5 will retract, but thegrippers 6,7 will not actuate.

After the main cylinder is fully retracted it is slid down the pipelineand placed in position to make the next joint. The process describedabove is then repeated.

The hydraulic power supply for this invention can be a gasoline ordiesel-driven hydraulic pump and a valve package to regulate thepressures as specified above. The power system is designed to supply upto 7 gallons per minute at a pressure less than 4000 psi, and up to 3.5gallons per minute at pressures between 4000 and 9000 psi. The powersupply, valve package, and the press all fit on top of a flat bedtrailer approximately 4 feet wide and 8 feet long.

While a specific embodiment of the invention is described hereinabove,it is understood that variations of the apparatus and method hereindescribed may be made within the scope and terms of the followingclaims.

We claim:
 1. A pipe coupling apparatus for press fitting the ends offirst and second sections of pipe together wherein the end of said firstpipe section has an internal diameter slightly less than the externaldiameter of the end of said second pipe section, said apparatuscomprising:two grippers each of which fits in the end sections of saidfirst and second pipes to be joined and frictionally engages theinterior walls of said pipes; and means for drawing said grippers towardone another until the exterior surface of said second pipe sectionfrictionally engages the interior surface of said first pipe section,thereby effecting a press fit joint between said pipes.
 2. A pipecoupling apparatus for press fitting the ends of first and second pipesections into a coupling disposed between said ends and containingapertures for receiving said ends, said apparatus comprising:twogrippers each of which fits in the ends of said first and secondsections of pipe to be joined and frictionally engages the interiorwalls of said pipes; and means for drawing said grippers toward oneanother until the exterior surfaces of said first and second pipesections engage the interior surfaces of said apertures, therebyeffecting press fit joints between said first pipe section and saidcoupling and between said second pipe section and said coupling.
 3. Apipe coupling apparatus according to either of claims 1 or 2 whereinsaid means for drawing said grippers toward one another furthercomprises:a hydraulic actuator connected to said grippers; a hydraulicpower source; and fluid communication means connecting said actuator andsaid source;whereby hydraulic power is transferred from said source tosaid actuator to move said grippers toward one another.
 4. A pipecoupling apparatus according to claim 3 wherein said hydraulic actuatorcomprises a hydraulic ram having a cylinder connected to one gripper anda piston with piston rod connected to said other gripper.
 5. A pipecoupling apparatus according to either of claims 1 or 2 wherein saidgrippers further comprise:a mandrel which can be inserted in the end ofsaid pipe; a plurality of slip pads arranged concentrically around theaxis of said mandrel; and a means for extending said slip pads radiallyoutward from said mandrel until said slip pads frictionally engage theinterior walls of said pipes.
 6. A pipe coupling apparatus according toclaim 5 wherein said means for extending said slip pads furthercomprises:exterior surfaces on said mandrel inclined in relation to theaxis of said mandrel; and an inclined surface on the back of said slippads which is inclined at a reverse angle to said mandrel exteriorsurfaces and is in contact with said mandrel exterior surface;wherebyrelative axial motion between said mandrel and said slip pads along theaxis of said pipe causes said slip pads to extend radially away fromsaid axis until said slip pads frictionally engage the interior wall ofsaid pipe or to retract radially away from the interior wall of saidpipe allowing said apparatus to be moved and positioned within saidpipe.
 7. A pipe coupling apparatus according to claim 6 wherein saidmandrel contains a plurality of low friction devices mounted on theexterior of said mandrel at a position radially further distant from theaxis of said mandrel than said slip pads when said slip pads are in theretracted position whereby said apparatus can be moved axially withinsaid pipe using minimal force.
 8. A pipe coupling apparatus for pressfitting the ends of a plurality of pipe sections into a hollow couplinghaving a plurality of ends, each end containing an aperture forreceiving one of said pipe section ends, said apparatus comprising:ahollow, pipe coupling adaptor having an elongated section shaped to fitwithin one of said apertures and a raised shoulder on the exteriorthereof for abutting an end of said coupling; at least two grippers oneof which fits in the end section of one of said pipe sections and one ofwhich fits within the hollow section of said adapter disposed in saidaperture of said coupling, said grippers frictionally engaging theinterior walls of said pipe and said adapter; and means for drawing saidgrippers toward one another; whereby the end of said pipe section ispress fit into said coupling.
 9. A pipe coupling apparatus according toclaim 8 wherein said means for drawing said grippers toward one anotherfurther comprises:a hydraulic actuator connected to said grippers; ahydraulic power source; and fluid communication means connecting saidactuator and said source;whereby hydraulic power is transferred fromsaid source to said actuator to move said grippers toward one another.10. A pipe coupling apparatus according to claim 9 wherein saidhydraulic actuator comprises a hydraulic ram having a cylinder connectedto one gripper and a piston with piston rod connected to said othergripper.
 11. A pipe coupling apparatus according to claim 9 wherein saidmeans for extending said slip pads further comprises:exterior surfaceson said mandrel inclined in relation to the axis of said mandrel; and aninclined surface on the back of said slip pads which is inclined at areverse angle to said mandrel exterior surface and is in contact withsaid mandrel exterior surface; whereby relative axial motion betweensaid mandrel and said slip pads along the axis of said pipe causes saidslip pads to extend radially away from said axis until said slip padsfrictionally engage the interior wall of said pipe or said adaptor or toretract radially away from the interior wall of said pipe allowing saidapparatus to be moved and positioned within said pipe or said adaptor.12. A pipe coupling apparatus according to claim 11 wherein said mandrelcontains a plurality of low friction devices mounted on the exterior ofsaid mandrel at a position radially further distant from the axis ofsaid mandrel than said slip pads when said slip pads are in theretracted position whereby said apparatus can be moved axially withinsaid pipe or said adaptor using minimal force.
 13. A pipe couplingapparatus according to claim 8 wherein said grippers further comprise:amandrel which can be inserted in the end of said pipe or said adaptor; aplurality of slip pads arranged concentrically around the axis of saidmandrel; and a means for extending said slip pads radially outward fromsaid mandrel until said slip pads frictionally engage the interior wallsof said pipes.